Internal gear wheel pump

ABSTRACT

The invention relates to an internal gear pump for pumping fuel from a suction conduit ( 18 ) into a pressure conduit ( 19 ), having a pump housing ( 1 ) in which an internal ring gear ( 5 ) and an externally toothed pinion ( 3 ), the latter driven by a drive shaft ( 2 ), are supported, the pinion ( 3 ) being disposed eccentrically to the ring gear ( 5 ) and cooperating with the ring gear ( 5 ) to generate a pumping action, and the pinion ( 3 ) and the ring gear ( 5 ) rest with their one face end on the pump housing ( 1 ) and with their other face end on a sealing plate ( 13 ).  
     To lengthen the service life of the internal gear pump, the suction conduit ( 18 ) is disposed in the sealing plate ( 13 ). The sealing plate ( 13 ) is movable relative to the pump housing ( 1 ) in such a way that the spacing between the suction conduit ( 18 ) and the pressure conduit ( 19 ) can be varied.

PRIOR ART

[0001] The invention relates to an internal gear pump for pumping fuelfrom a suction conduit into a pressure conduit, having a pump housing inwhich an internal ring gear and an externally toothed pinion, the latterdriven by a drive shaft, are supported, the pinion being disposedeccentrically to the ring gear and cooperating with the ring gear togenerate a pumping action, and the pinion and the ring gear rest withtheir one face end on the pump housing and with their other face end ona sealing plate.

[0002] An internal gear pump of this kind is also called a ring gearpump or gear-rotor pump. The ring gear and the pinion represent the pumpelements and are also called the outer rotor and the inner rotor,respectively. In German Patent Disclosure DE 38 27 573 A1, an internalgear pump is described whose ring gear is driven via an electric motor.The pumping chambers of the internal gear pump that are located betweenthe sets of teeth of the two pump elements are covered in the axialdirection by a pressure plate. A helical spring, embodied as acompression spring, which is prestressed against the pressure plateassures that the axial play equals zero when the internal combustionengine is started.

[0003] When an internal combustion engine is operated with an internalgear pump of this kind, it has been found that upon engine starting, themaximum pumping capacity of the internal gear pump is required. Once theengine has reached its full rpm, a lesser pumping capacity suffices toassure an adequate fuel supply to the engine.

[0004] The object of the invention is to furnish an internal gear pumpof the type defined at the outset, which has zero axial play at startingrpm and whose pumping capacity decreases once the starting rpm has beenexceeded. It should be possible to produce the internal gear pump of theinvention economically, and the pump should have a long service life.

[0005] In an internal gear pump for pumping fuel from a suction conduitinto a pressure conduit, having a pump housing in which an internal ringgear and an externally toothed pinion, the latter driven by a driveshaft, are supported, the pinion being disposed eccentrically to thering gear and cooperating with the ring gear to generate a pumpingaction, and the pinion and the ring gear rest with their one face end onthe pump housing and with their other face end on a sealing plate, thisobject is attained in that the suction conduit is disposed in thesealing plate, and that the sealing plate is movable relative to thepump housing in such a way that the spacing between the suction conduitand the pressure conduit can be varied.

ADVANTAGES OF THE INVENTION

[0006] If the spacing between the suction conduit and the pressureconduit is decreased, the consequence is that the pumping capacity ofthe internal gear pump decreases. This offers the advantage that anintake throttle, required in conventional internal gear pumps, can bedispensed with.

[0007] A particular feature of the invention is characterized in thatthe suction conduit is formed by an elongated recess in thecircumferential direction of the sealing plate, and that the sealingplate is rotatable relative to the pump housing between two points.

[0008] A further particular feature of the invention is characterized inthat the sealing plate is prestressed in the axial direction with theaid of a spring, which is coupled to the pump housing and to the sealingplate. By the spring prestressing in the axial direction, it is attainedthat a motion of the sealing plate in the axial direction does not occuruntil a certain pressure in the pump chamber has been exceeded.

[0009] A further particular feature of the invention is characterized inthat the spring is prestressed in the circumferential direction counterto the driving direction of the internal gear pump. Because of thespring prestressing in the circumferential direction, it is attainedthat the sealing plate does not rotate until a certain rpm of the pinionhas been exceeded.

[0010] A further particular feature of the invention is characterized inthat the spring includes two curved legs, which on one end are joinedtogether and coupled to the sealing plate, and on the other end arecoupled to the pump housing. By the design according to the invention ofthe spring, a prestressing of the spring both in the axial direction andin the circumferential direction is made possible by simple means.

[0011] A further particular feature of the invention is characterized inthat on the side of the sealing plate remote from the ring gear and thepinion, a pin is guided axially displaceably at a certain spacing, whichpin cooperates with a further spring in order to counteract a motion ofthe sealing plate in the axial direction. The spacing between thesealing plate and the pin is selected such that the sealing plate comesto rest on one face end of the pin in full-load operation. If thepressure in the pump chamber rises further, the sealing plate movesfarther counter to the prestressing force of the further spring. Theprestressing force of the further spring, its spring rate, and thedisplacement of the sealing plate in the axial direction up to a stopdefine the maximum operating pressure of the internal gear pump.

[0012] A further particular version of the invention is characterized inthat the suction conduit communicates with a fuel inlet, whoselongitudinal axis coincides with the longitudinal axis of the driveshaft. This design has proved to be especially advantageous in practice.

[0013] A further particular feature of the invention is characterized inthat the fuel inlet discharges into a sleeve, in which the furtherspring is received, and in which radial bores are mounted for thepassage therethrough of fuel. The sleeve forms a stop that defines theaxial motion of the sealing plate.

[0014] A further particular feature of the invention is characterized inthat a bypass valve is accommodated in the pump housing and communicateswith the suction conduit via a first axial bore and with the pressureconduit via a second axial bore. Within the context of the presentinvention, “axial” means in the direction of the longitudinal axis ofthe drive shaft of the internal gear pump. The bypass valve makes itpossible, for instance with the aid of an additional hand-actuated pump,to pump the fuel in a way that bypasses the internal gear pump when theinternal gear pump is not being driven.

[0015] Further advantages, characteristics and details of the inventionwill become apparent from the ensuing description, in which oneexemplary embodiment of the invention is described in detail inconjunction with the drawing. The characteristics recited in the claimsand mentioned in the description can each be essential to the inventionindividually or in arbitrary combination.

DRAWING

[0016] Shown in the drawing are:

[0017]FIG. 1, one embodiment of an internal gear pump of the inventionin longitudinal section;

[0018]FIG. 2, the elevation view of a section taken along the line II-IIin FIG. 1;

[0019]FIG. 3 the elevation view of a section taken along the lineIII-III in FIG. 1; and

[0020]FIG. 4, the elevation view of a section taken along the line IV-IVin FIG. 1.

[0021] The internal gear pump shown in FIGS. 1-4 includes a pump housing1. A drive shaft 2 is rotatably supported in the pump housing 1. Withthe drive shaft 2, an internal gear or pinion 3 is driven, which ismounted on the end of the drive shaft 2 with the aid of a tolerance ring4. Internal gear 3 is in engagement with an external gear 5, which isalso known as a ring gear. The external gear 5 is surrounded by abearing ring 6, which is secured to the pump housing 1 with the aid ofscrews 7 and 8. The heads of the screws 7 and 8 are marked 9 and 10.

[0022] With the aid of a cup spring 12, which is braced against a Seegerring 11 that is secured in a groove of the drive shaft 2, the driveshaft 2 is prestressed to the left, away from the internal gear 3. Bythe prestressing force of the cup spring 12, the internal gear 3 is keptin contact with the pump housing 1. A sealing plate 13 rests on theother face end of the gears 3 and 5. The sealing plate 13 is kept incontact with the gears 3 and 5 with the aid of a spring 14. As FIG. 3shows, the spring 14 includes two curved legs 15 and 16. Two bent-overends of the curved legs 15 and 16 are received in a blind bore 27 of thesealing plate 13. The two other ends of the legs 15 and 16 are securedto the screw heads 9 and 10 and thus to the pump housing 1.

[0023] In FIG. 4, the direction of rotation of the drive shaft 2 isrepresented by an arrow 34. When the internal gear 3 is driven in thedirection of the arrow 34, the fuel located in the pressure chamber 17is compressed. Simultaneously, as can be seen in FIG. 3, fuel isaspirated from a suction conduit 18, which is recessed out of thesealing plate 13. The aspirated fuel is compressed in the pressurechamber 17 and then reaches a pressure conduit 19, which, as indicatedby dashed lines in FIG. 3, is recessed out of the pump housing 1.

[0024] The suction conduit 18 and the pressure conduit 19 communicatevia connecting bores 21 and 20 with a bypass valve 22. When thepre-stressed check valve 22 is opened, the two connecting bores 20 and21 are in communication with one another. When the bypass valve 22 isclosed, the communication between the connecting bores 20 and 21 isclosed, and the pressure conduit 19 communicates with a pressureconnection 23 via the connecting bore 20.

[0025] The suction conduit recessed out of the sealing plate 13communicates with a suction chamber 24, which is surrounded by a housingcap 35. The housing cap 35 is seated on the pump housing 1. A centralfuel inlet bore 36 is recessed out of the housing cap 35.

[0026] Two rectangular recesses are provided, diametrically opposite oneanother, on the outer circumference of the sealing plate 13. The twoopposite sides of the recesses, together with the screw heads 9 and 10,form stops 25 and 26 for a rotary motion of the sealing plate 13. In theposition of the sealing plate 13 as shown in FIG. 3, the stop faces 26are in contact with the screw heads 9 and 10. An arrow 44 indicates thatthe sealing plate 13 rotates, with increasing rpm of the drive shaft 2,until the stop faces 25 rest on the screw heads 9 and 10.

[0027] In FIG. 1, it can be seen that a pin 28 is disposed on the sideof the sealing plate 13 remote from the drive shaft 2. Between thesealing plate 13 and one face end of the pin 28, a certain spacing isprovided. The pin 28 is subjected to the prestressing force of acompression spring 29 that is received in a sleeve 30. The pin 28 isalso guided displaceably in the axial direction in the sleeve 30. Thesleeve 30 is secured in the interior of the housing cap 35, coaxially tothe fuel inlet bore 36. Bores 31 and 32 are recessed out of the jacketface of the sleeve 30, in order to assure the passage of fuel from thefuel inlet 36 into the suction chamber 24.

[0028] The internal gear 3 of the pump is driven by the drive shaft 2and the tolerance ring 4. The cup spring 12 also keeps the internal gear3 in contact with the plane face of the pump housing 1 counter to anaxial force inward from the drive coupling that might possibly occur.The pump housing 1 supports the drive shaft 2 and includes the pressureconduit 13, the connecting bore 20 to the pressure connection 23, andthe bypass valve 22. The bore 21 connects the bypass valve 22 to thesuction chamber 24 of the internal gear pump and makes it possible, forinstance by means of a hand-actuated pump, to pump the fuel in a waythat bypasses the pump elements if the internal gear pump is not beingdriven.

[0029] The pump housing 1 supports the external gear 5 with the aid ofthe bearing ring 6. In the starting state, the sealing plate 13 isplaced without play against the gears 3 and 5 and is pressed slightly bythe spring 14. The force of the spring 14 is designed, for starting theinternal gear pump, in such a way that an adequate fuel pressure forfilling the low-pressure system is assured.

[0030] The second function of the spring 14 is to keep the sealing plate13 in a position rotated relative to the direction of rotation of thegear during starting. This position guarantees the maximum supplyquantity at starting rpm. Accordingly, the sealing plate 13 is pressedby the spring 14 against the stop 26, embodied as the screw head 10,counter to the direction of rotation of the gear. The plate 13 has nocontact with the bearing ring 6, which is achieved by means of a play ofapproximately 0.01 mm.

[0031] When the rpm rises and the flow through the suction conduit 18reaches the idling quantity, the plate 13 rotates, until the oppositestop face 25 rests on the screw head 10. This brings about a limitationof the supply quantity as the rpm rises. Hence no intake throttling ofthe pump is necessary, which reduces the tendency to cavitation. Infull-load operation, the sealing plate 13 presses against the pin 28.When the pressure in the pressure chamber 17 reaches a limit value, theplate 13 moves farther to the right and presses against the spring 29,via the pin 28.

1. An internal gear pump for pumping fuel from a suction conduit (18)into a pressure conduit (19), having a pump housing (1) in which aninternal ring gear (5) and an externally toothed pinion (3), the latterdriven by a drive shaft (2), are supported, the pinion (3) beingdisposed eccentrically to the ring gear (5) and cooperating with thering gear (5) to generate a pumping action, and the pinion (3) and thering gear (5) rest with their one face end on the pump housing (1) andwith their other face end on a sealing plate (13), characterized in thatthe suction conduit (18) is disposed in the sealing plate (13), and thatthe sealing plate (13) is movable relative to the pump housing (1) insuch a way that the spacing between the suction conduit (18) and thepressure conduit (19) can be varied.
 2. The internal gear pump of claim1, characterized in that the suction conduit (18) is formed by anelongated recess in the circumferential direction of the sealing plate(13), and that the sealing plate (13) is rotatable relative to the pumphousing (1) between two points.
 3. The internal gear pump of claim 2,characterized in that the sealing plate (13) is prestressed in the axialdirection with the aid of a spring (14), which is coupled to the pumphousing (1) and to the sealing plate (13).
 4. The internal gear pump ofclaim 3, characterized in that the spring (14) is prestressed in thecircumferential direction counter to the driving direction of theinternal gear pump.
 5. The internal gear pump of claim 3 or 4,characterized in that the spring (14) includes two curved legs (15, 16),which on one end are joined together and coupled to the sealing plate(13), and on the other end are coupled to the pump housing (1).
 6. Theinternal gear pump of one of claims 3-5, characterized in that on theside of the sealing plate (3) remote from the ring gear (5) and thepinion (3), a pin (28) is guided axially displaceably at a certainspacing, which pin cooperates with a further spring (29) in order tocounteract a motion of the sealing plate (13) in the axial direction. 7.The internal gear pump of one of the foregoing claims, characterized inthat the suction conduit (18) communicates with a fuel inlet (36), whoselongitudinal axis coincides with the longitudinal axis of the driveshaft (2).
 8. The internal gear pump of claim 7, characterized in thatthe fuel inlet (36) discharges into a sleeve, in which the furtherspring (29) is received, and in which radial bores (31, 32) are mountedfor the passage therethrough of fuel.
 9. The internal gear pump of oneof the foregoing claims, characterized in that a bypass valve (22) isaccommodated in the pump housing and communicates with the suctionconduit (18) via a first axial bore (21) and with the pressure conduit(19) via a second axial bore (20).